Deformations and cracking obtained through digital image correlation on fibre reinforced concrete subjected to shear

The contributions of fibre reinforced concrete can be considered in structural design. In order to do so, the standards have established certain requirements that permit reducing partially or even totally the steel bars. Such requirements are based on residual tensile strengths obtained by three or four point bending tests. This tensile strengths might not be suitable to be applied to any other type of stress to which the material can be subjected. Fibres can bridge the concrete crack, preventing the crack growth andgenerating a network of cracks with shorter and thinner that improve the material's behaviour when subjected to bending or shear stresses as well as thedurability of the element. This reinforcement technique was developed with the use of steel fibres. In recent years, the use of macro-polymer fibres has become an attractive alternative due to the absence of corrosion and other operational advantages.At the time of writing, it is still important to understand the resistant mechanismsof fibre reinforced concrete elements subjected to shear stresses according to shear-friction theory, such as aggregate interlock and the dowel action of the rods or fibres that seal the crack.Having that said, the main objective of this study was to analyse the different cracking patterns that occurred in fibre reinforced concrete specimens subjected to shear stress and to obtain the displacements on the cracks. In order to achieve these objectives push-off specimens, obtained from residual halves of bending specimens, were tested. The tests were performed by using a digital image correlation system that allowed the cracks on the faces of the specimens to be monitored as shown in Figure 1. Four concrete types were used for the tests: one reinforced with 0.66% volume fraction of polyolefin fibres, the second with 1.10% volume of polyolefin fibres and the others reinforced with 0.64 and 0.90% of steel fibres. According to the results of the tests, the cracking patterns were obtained as well as the displacements on the crack in reference to the shear-friction theory